The urinary tract is one of the commonest sites for bacterial infection. Strains of E. coli are responsible for greater than 80-90% of these episodes. Urinary tract infections in young women account for an estimated 7 million office visits per annum and more thana billion dollars of direct medical costs. Further, 20% of women will develop frequent recurrences. Understanding the mechanisms through which recurrences occur and devising preventative strategies is thus of considerable importance and is presently poorly understood. We utilized pulsed-field gel electrophoresis, to evaluate E. coli strains prospectively collected from 23 women with recurrent urinary tract infections. A subgroup of 6 women was studied to determine whether bacterial persistence within the urinary tract occurs or whether the colon is a reservoir for reinfecting strains. We determined that: 1 ) Genotypes of isolates from a given individual with recurrent urinary tract infections are the same the majority of the time. 2)The majority of recurrences are due to bacterial reinfection, not persistence. 3)The faeces serves as the reservoir for re-infecting strains. These results have significant therapeutic implications for women with recurrent UTI. This project has been terminated at N.I.H.